Inflatable mattress



FIG. 1 is a perspective view of the inflatable mattress showing the new design;

FIG. 2 is a front view of the new design;

FIG. 3 is a rear view of the new design;

FIG. 4 is a left view of the new design;

FIG. 5 is a right view of the new design;

FIG. 6 is a top view of the new design; and,

FIG. 7 is a bottom view of the new design. 

The ornamental design for a inflatable mattress, as shown and described. 